Since a speaker generates sound waves by the vibration of diaphragm, the phases are shifted 180 degree between a vibration generated in front of the diaphragm and a vibration generated at the back. Therefore, in order to obtain good frequency characteristics and efficiency, it is necessary to avoid that the vibration generated at the back does not interfere with the vibration generated in front. As a fundamental structure, a sealed space or an almost sealed space is needed at the back.
Moreover, in a device in that the area to attach a speaker cannot be sufficiently secured as a front panel of a television receiving set, a sealed or a semi-sealed space is secured by placing the main body of a speaker in the back space of a cabinet of a television receiving set. And a technique to lead sound waves generated in front of a diaphragm to the front panel of the television receiving set by a waveguide is taken.
For example, in the Patent Publication No. 3449571, in FIG. 5, an example that a speaker is set in the back space of a cabinet of a television receiving set, and sound is led to the front panel of the television receiving set by a waveguide has been introduced.
Moreover, in FIG. 6 in the same patent, an example that a speaker is attached to a back cabinet (sealed box) in the device of FIG. 5 been introduced.
Moreover, in FIGS. 1 to 4 in the same patent, a television receiving set in which a sound at the back of a diaphragm of a speaker is radiated diagonally forward by a reflecting member, and avoiding the interference between a sound in front of the diaphragm and the sound at the back has been introduced.    Patent Document 1: Patent Publication No. 3449571